Combustion Dynamics of Swirl Coaxial Injectors in Fuel-Rich Combustion

An experimental study was carried out to investigate the combustion characteristics of liquid–liquid swirl coaxial injectors in a fuel-rich gas generator. Propellants of liquid oxygen and kerosene (jet A-1) were burned in a range of mixture ratios (0:29 0:38) and chamber pressures (53:6 57:9 bar) in several combustion chambers with differentdiametersandlengths.Aninjectorheadhad37identicalswirlcoaxialinjectorswithlargerecesslengthsand internal-mixingcharacteristics.Theinjectorheadwasconnectedtocombustionchambersandachokednozzleeither with or without an extension pipe. It was found that the combustion characteristic velocity, combustion gas temperature, and combustion dynamics were seldom influenced by the increase of injector recess length in the present fuel-rich conditions. The results of dynamic pressure data and swirl-injector dynamics suggest that the longitudinal-modecombustioninstabilityinthefuel-richgasgeneratorequippedwithbiswirlcoaxialinjectorscould besignificantlyaffected bytherelationship betweenthe resonant frequencyin thecombustion chamberandthe flow dynamics of the swirl injector.